This invention relates to fuel injection pumps for internal combustion engines capable of effecting control of the amount of fuel injected and the injection timing, and, more particularly, to a fuel injection pump for an internal combustion engine comprising a rotor located in a housing, a free piston movably mounted in an axial bore in the rotor, two pressure chambers defined by an inner wall surface of the axial bore in the rotor and the free piston, and two solenoid valves for supplying fuel to the two pressure chambers.
Fuel injection pumps are used for feeding fuel at high pressure into the interior of internal combustion engines. In recent years, a demand has been created for relying on electronic control for effecting control of the amount of the fuel injected and the injection timing of a fuel injection pump. A device of this type is shown, for example, in U.S. Pat. No. 4,185,779.
In the fuel injection pump incorporating therein the control device of this type, control of the amount of the fuel injected and the injection timing are effected by feedback control utilizing the servomechanism. The device of this type is complex in construction and high in cost.
In, for example, commonly assigned U.S. Application Ser. No. 304,359, and now U.S. Pat. No. 4,445,822 a fuel injection pump capable of readily controlling both the amount of the fuel injected and the injection timing is described wherein the fuel injection pump comprises a rotor located in a cylindrical housing, a free piston movably mounted in an axial bore in the rotor, two pressure chambers defined by an inner wall surface of the axial bore in the rotor and the free piston, and two solenoid valves for supplying fuel to the two pressure chambers. One of the two pressure chambers receives therein the fuel to be injected and the other pressure chamber receives therein the fuel for effecting control of the injection timing. The two pressure chambers are separated from each other by the movable free piston.
The fuel injection pump described hereinabove is capable of readily controlling the amount of the fuel injected and the injection timing by virture of the aforesaid construction. However, a lack of means for sensing the amount of fuel drawn by suction to be injected and the timing for compressing the fuel to be injected, it has been impossible to directly detect abnormal conditions of the fuel injection pump, such as trouble of the solenoid valves.